For example, Japanese Unexamined Patent Application Publication No. 07-187019 (Patent Literature 1 (PTL 1)) (Claim 1, FIG. 1) discloses a vehicle body side portion structure including an extension member that includes a connecting portion and an enlargement portion. The connecting portion is connected to a rear end portion of a front side member. The enlargement portion is formed continuously with the connecting portion and extends towards the rear of the vehicle body. In addition, the enlargement portion becomes wider in a vehicle width direction and is joined to a side sill. The extension member is joined to a region extending from a rear end portion of the front side member to a dash lower panel and to a floor panel. A plurality of reinforcing beads extending in a front-rear direction of the vehicle body are formed in the enlargement-portion substantially in parallel in the vehicle width direction. In PTL 1, it is possible to disperse and transmit a collision input occurring at the time of a head-on collision to the floor panel.
Although, in the vehicle body side portion structure described in the aforementioned PTL 1, it is possible to disperse and transmit a collision input occurring at the time of a head-on collision to the floor panel, a collision load that is generated in a side collision of a vehicle cannot be properly absorbed. In particular, in a vehicle in which an energy storage, such as a fuel tank or a battery, is disposed at a central portion of the vehicle body, a vehicle body side portion structure that reduces a collision load that is generated in a side collision of a vehicle is desired.